Such stars tend to avoid orchestral subscription concerts because they don't like to sing on consecutive nights. Yet the Verdians will sing for Nézet-Séguin Friday through Sunday anyway, as will a different lineup of soloists in March when he conducts Bach's St. Matthew Passion on three consecutive nights.
A major gap in Philadelphia's musical life is being filled. Singers of Fleming's caliber are usually out of reach financially for Opera Company of Philadelphia and the Philadelphia Chamber Music Society. The Kimmel no longer presents large-hall vocal recitals.
Now, Nézet-Séguin's love of choral repertoire is opening a window of opportunity - "which is fantastic," said Kimmel Center CEO Anne Ewers. "There are extraordinary voices out there, but audiences tend not to be interested in recitals. But a chance to hear these vocalists with Yannick . . . we're very excited."
Riccardo Muti used to pull off vocal casting coups; Wolfgang Sawallisch tried but was stymied by cancellations. So far, Nézet-Séguin, 37, seems blessed in that regard. Might he be the Diva Whisperer? He even selected Fleming's opening-night repertoire - such non-gala-ish fare as Ravel's Shéhérazade and music from Richard Strauss' Arabella.
"He's almost balletic in showing us what he wants," said Fleming. "It's a lot about breath - we are wind instruments, after all - and at certain points when a singer runs out of steam, he'll meet us halfway" and speed up the phrase. She has but one reservation: "It's almost disconcerting when the conductor has all the words memorized."
Is it any surprise they're planning to work together in Dvorak's Rusalka at the Met? Nézet-Séguin conducts there annually, and he's also bonded with Poplavskaya. Villazon is part of his Mozart opera recording project with Deutsche Grammophon. These people are his friends.
Much of diva whispering comes from the conductor's understanding of what singers go through before arriving at rehearsal: "Because the voice is inside the body, the training involves many people telling them what to do. Voice coaches. Language coaches," he said in a phone interview last week.
At one time, he was one of those people, a choral coach; now he wants to be a haven from that, starting with one-on-one rehearsals: "It's much better to let the trust develop naturally and show the singer there's a line and structure to what I'm doing. And then after a week or two, we have meetings to discuss the psychology of the role."
Like many accomplished vocal conductors, his own pipes aren't great. During his early conducting years in his native Montreal, he filled in for a tenor in Bach's St. John Passion. The press wasn't kind.
Whatever. Vocal and choral music was in his blood beginning with his Roman Catholic upbringing. He coached choral rehearsals from the age of 12. He sketched scenes from the Bach passions. "This is the environment I've been in for all my life," he said.
By the time he arrived at the Westminster Choir College in Princeton for two summers in his late teens, Joseph Flummerfelt, doyen of choral conductors, says he immediately recognized "an innate sensitivity to how the gesture affects the sound."
The ease of movement Fleming discussed is also significant.
"It's important to rid any tension from the body," said Flummerfelt. "A lot of famous conductors don't get the whole range of choral and orchestral color because of the tension of the gesture. It comes back to what will allow the energy to flow most effortlessly from the conductor to his or her forces."
Most groups Nézet-Séguin headed in the mid- to late 1990s were vocally oriented: Choeur polyphonique de Montréal, Choeur de Laval, La Chapelle de Montréal (which he founded in 1995). For Opéra de Montréal, he was chorus master.
Local choral conductors don't need to know these resumé items; his performances say it all. David Hayes, who heads longtime orchestra collaborator the Philadelphia Singers Chorale, believes good choral conducting involves sensitivity to the text and vocal color, plus the ability to hear vowels out of alignment. "He has a strong sense of all those things," wrote Hayes in an e-mail regarding their collaboration on a 2011 Mozart Requiem. "He was always very clear about exactly the vocal color he was looking for," and also matched chorus and orchestral phrases.
"Yannick breathes," said Donald Nally, founder of the Crossing choir. "All great conductors carry the sound their ensembles make in their chest, in the breathing place where we are vulnerable, the place we cover up when disturbed. This is why you can instantanously identify certain conductors' sound."
Nézet-Séguin arrives in Philadelphia having conducted a dozen prevous Verdi Requiem performances. The music has some of the most graphic choral writing in the literature, dramatizing, among other things, the Last Judgment. To that, he brings much interior imagery: "I envision the Earth opening up into something as immense as the universe. You can fall into the depths of the abyss or you can reach the sky."
He requested the Westminster Choir for Verdi: It represents his conducting roots, and was used by Arturo Toscanini in his 1940 live Carnegie Hall recording of the piece.
The biggest test is out of his hands. Near the end, the Requiem scales down into a single, quiet high C for the solo soprano - great when sung perfectly, hugely embarrassing when flawed. Nézet-Séguin doesn't wonder whether Poplavskaya will nail it, but what shade of meaning she'll deliver.
"She thinks with text and color. She doesn't think vocally," he says. "I won't impose anything on her, just let her find it with her own voice.
"And that's still to be found out in the next few days!"
Contact David Patrick Stearns at email@example.com.